Symptoms of rat bite fever — which include fever, development of an ulcer at the bite wound, swelling near the wound, swollen lymph nodes and a rash — usually occur seven to 21 days after exposure to an infected rat.

"It's a means to ensure this doesn't happen again," Gomez said. "Apparently there was some breakdown in procedures. They want tighter controls."

Petco Animal Supplies Inc. told the Associated Press that the company was "in the process of investigating these claims and will respond appropriately when we have more information."

Petco expressed condolences to the Pankey family.

"We are deeply saddened by the Pankey family's tragic loss," Petco said in a statement. "The health and safety of people and pets is always a top priority, and we take the family's concerns very seriously."

"He was a bright, energetic, friendly, happy kid who actually had a prior rat, who was a female, and he had this idea in his young head of having his female rat get married," Gomez said of Aiden.